Alternatively, how can I start the ubuntuone GUI client from the terminal? Sorry if this is a dumb question - it seems to me that it should be obvious so probably I am just staring right at it but not seeing it. Thanks...

Is pre-installed (by default) and you can find it in System settings > Ubuntu One.

Alternatively you can open it in the terminal giving one of these commands:

ubuntuone-control-panel-qt or ubuntuone-installer

If you have no installation candidate then check if by mistake you disabled the main repositories. Open Ubuntu Software Center > Edit > Software Sources > Ubuntu Software and see if Canonical-supported free and open-source software (main) is marked.

You can run in terminal

sudo apt-get update
sudo apt-get upgrade

to ensure that your software is up to date.

At the gnome-classic environment (gnome-panel) you can add / remove applications to/from panel by pressing Super+Alt+ right click with the mouse cursor upon the panel (Super = Windows key) and you can add Ubuntu One icon there as well.